Japanese Team Achieves 8.8THz Laser Diode Tuning Range

Researchers at Tohoku University and the National Institute of Information and Communications Technology (NICT) in Japan, have developed a novel ultra-compact heterogeneous wavelength tunable laser diode. The heterogeneous laser diode was realised through a combination of silicon photonics and quantum-dot (QD) technology, and demonstrates a wide-range tuning-operation.

The researchers presented their work at a Conference on Lasers and Electro-Optics (CLEO) in San Jose, California, on May 13. The related paper was also published inApplied Physics Express.

Recent high-capacity optical transmission systems are based on wavelength-division multiplexing (WDM) systems with dense frequency channels. The frequency channels in C-band (conventional band: 1530- 1565nm) are overcrowded and the frequency use efficiency is saturated in such WDM systems. On the other hand, extensive and unexploited frequency resources are buried in near-infra-red wavelengths (1000-1300nm).

Additionally, photonic devices are required to have smaller footprints and lower power consumption in short-reach data transmission. The compact and low power consumption wavelength tunable laser diode is a key device to tap the undeveloped frequency bands for higher capacity data transmission systems, according to the researchers.

The heterogeneous wavelength tunable laser diode, consisting of the QD and the silicon photonics, is a promising candidate to realise such a compact and broad-band light source. This is because the QD has large optical gains of around 1000-1300nm wavelength, and silicon photonics provide a promising platform for highly integrated photonics devices - so a novel wavelength-tunable laser diode, combining QD and silicon photonics technologies, was proposed.

The cooperative research group led by Tomohiro Kita and Naokatsu Yamamoto demonstrated a wide range tuning operation of around 1250nm wavelength with an ultra-small device footprint. The obtained frequency tuning-range of 8.8THz is said to be a world record for the category of QD and silicon photonics heterogeneous wavelength tunable laser diodes.

It is expected that the fusing of the QD technology and silicon photonics will provide a breakthrough for the development of an effective and compact light source.

This research was partially supported by the Strategic Information and Communications R&D Promotion Program (SCOPE) of Japan's Ministry of Internal Affairs and Communications.